Subduction And Closure Of The Palaeo Asian Ocean Along The Solonker Suture Zone Constraints From An Integrated Sedimentary Provenance Analysis

This Ph.D. thesis attempts to decipher the closure of the Palaeozoic Palaeo-Asian Ocean along the enigmatic Solonker Suture in East Asia adopting a methodology that integrates geochemical and geochronological data from Palaeozoic sedimentary and volcanic rocks in the region. It provides an in-detail but also broad insight into the Palaeozoic to early Mesozoic tectonic evolution of the region, not only pin-pointing the debated location of the Solonker Suture but also the timing of final disappearance of the Palaeo-Asian Ocean during Permian to Early Triassic times. The results have led to propose a tectonic ‘soft-collision’ model for the amalgamation of the North China Craton and the Mongolian Terranes in northern Asia explaining the general absence of geologic features characteristic for continent-continent collisions such as the occurrence of regional-scale high-grade metamorphic rocks, ophiolite belts and fold-thrust structures. This new model may serve as a blueprint for the tectonic evolution of similar suture zones that are characterized by the absence of typical collision related lithologies and structures. The thesis is particularly useful as a guide for researchers who seek an in-depth understanding of the Palaeozoic to early Mesozoic tectonic evolution of northern China and Central Asia along the Solonker Suture.

This dissertation, "Subduction and Closure of the Palaeo-Asian Ocean Along the Solonker Suture Zone: Constraints From an Integrated Sedimentary Provenance Analysis" by Paul Reinhold, Eizenhöefer, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: The Central Asian Orogenic Belt formed by accretion subsequent to the contraction of the Palaeo-Asian Ocean that ultimately disappeared along the Solonker Suture Zone in East Asia. Since typical regional collisional features are absent, the tectonic evolution of the suture remains speculative. Integrated sedimentary provenance analyses across the accretionary collision zone between the Mongolian Arcs and the North China Craton place new constraints on the events that led to final suturing. An investigation on the geochronological and geochemical variability in Permian strata along a southeast-northwest transect revealed distinct differences across the Solonker Suture Zone: northern basins carry a broad Mesoproterozoic to latest Precambrian age signature, and their provenance terranes are of mixed juvenile to crustal magmatic origin. In contrast, southern basins contain detritus from the North China Craton, and their sources are of dominantly crustal contaminated magmatic origin. Provenance analysis suggests, that in the Early Palaeozoic (ca. 429 Ma) the Palaeo-Asian Ocean was consumed along the Uliastai Arc and the North China Craton, initiating the formation of the Northern and Southern Accretionary Orogens, respectively. By the end of the Middle Carboniferous the Mongolian Arcs consolidated after accretion of the Uliastai Arc. In the Late Carboniferous (ca. 314 Ma) the Hegenshan back-arc basin opened, detaching the Northern Accretionary Orogen. While subduction continued there, it may have temporarily ceased along the Southern Accretionary Orogen after accretion of a microcontinent (ca. 300 Ma). During the Middle Permian back-arc basin closure led to the formation and obduction of the Hegenshan supra-subduction zone ophiolite. Eventually, the Palaeo-Asian Ocean closed after wedge-wedge collision, which would not involve continental deep subduction, thus, leading to cryptic suturing from the Late Permian to Early Triassic. Statistical analyses on the heterogeneity and similarity of the age probability density functions require a complex Permian palaeo-geographic setting, involving a variety of arc basins, which received sediments dependent on the contemporary arc geometry. Early stages of the sequence likely resembled a Pacific-type scenario, including Japan-type back-arc basin opening, whereas the late stages were similar to the archipelago-type setting of present-day Southeast Asia. Subjects: Suture zones (Structural geology) - China - Inner Mongolia

This book presents a complete set of studies of alluvial fan sediments in southern Iran from the point of view of sedimentology, sedimentary geochemistry, tectonics, economic geology, groundwater, geomorphology, hazards and telemetry. In addition, the book focuses on advanced topics and theory, which practically serves as a model for the study of this type of sediment around the world. Alluvial fans are an important and fundamental factor in many sciences such as geology, environmental science, natural hazards, groundwater science, agriculture and many other related sciences. Lack of accurate knowledge of their constituent sediments has always been an important problem for experts in many science disciplines. From the economic point of view, the identification of alluvial fan deposits is of particular importance. For example, alluvial deposits are the centre of groundwater accumulation, and most groundwater reservoirs within the sedimentary basin are fed by water from alluvial deposits. Most of the gold production in South Africa has been formed as placer deposits in ancient alluvial fans. In addition, a large amount of uranium placer deposits is extracted from old alluvial fans in sedimentary basins in South Africa. This book serves as an ideal guide for experts in earth and environmental sciences and hydrology.

The Tethyan orogenic belt extends from the western Mediterranean to southeast Asia and the exposed rocks and landscapes present today are records of multiple orogenic events. The most recent, the Alpine-Himalayan orogeny, evolved during the Mesozoic-Cenozoic closure of the Neotethys Ocean during the convergence of Gondwana with Laurasia. Over the last few decades, significant advances in geochemical and geochronological methods and their widespread application have created a high-resolution temporal framework that reveals that various proxy records of intercontinental collisions across the Alpine-Himalayan belt differ by tens of millions of years. Consequently, new questions have arisen, including how to unite these seemingly disparate records of subduction and collision into a temporally and spatially credible reconstruction.The work set forth in this dissertation situates the Anatolian segment of the Alpine-Himalayan orogenic belt in the broader discussion on the timescales and drivers of intercontinental collisions and their effect on biogeography. The various suture zones in Anatolia that delineate former branches of the Neotethys Ocean have complex and unresolved geodynamic reconstructions, including single and double subduction systems, pre-collisional subduction of lower plate terranes, forearc and backarc extension, ophiolite obduction, and protracted collisional deformation. Resolving these competing geodynamic scenarios is essential for paleogeographic reconstructions for refining the mechanistic links between subduction, accretion, and collision processes. Furthermore, the role of collisions in the early Cenozoic Anatolian archipelago in facilitating mammalian faunal exchange, including anthropoid primates, between Europe, Asia and Africa relies on accurate paleogeographic and topographic reconstructions. Near-continuous deposition in western Anatolian sedimentary basins preserves an unbroken record of subduction through collision that is unparalleled across the Tethyan realm. This dissertation utilizes this sedimentary record by providing new stratigraphic, sedimentologic, petro- and geochronologic, and sedimentary provenance constraints on the chronology of collision along the İzmir-Ankara-Erzincansuture zone and the Intra-Pontide suture zone in western Anatolia. The sedimentary basin reconstructions presented in this dissertation, synthesized with existing datasets, provide a model for multi-stage continental collision that is applicable across the Tethyan realm. Detrital zircon U-Pb geochronology and sandstone petrography data from the forearc-foreland Central Sakarya Basin in western Anatolia indicate that collision along the İzmir-Ankara-Erzincan suture zone began at 76 Ma, recorded as a major shift in provenance and the onset of exhumation, sediment recycling, and suture zone uplift. Furthermore, new stratigraphy, sedimentology and sedimentary provenance studies from the foreland Sarıcakaya Basin in western Anatolia reveal that significant upper plate deformation was delayed by 20 Myr. By 54 Ma, the Central Sakarya Basin was partitioned by a basement-involved thrust fault, and flexural loading from the thrust created the Sarıcakaya Basin. This 20 Myr protracted collision along the İzmir-Ankara-Erzincan suture zone can be explained by three Tethyan models for multi-stage collision: slab breakoff, relict basin closure, or subduction of thinned passive margin lithosphere. The validity of relict basin closure is evaluated using detrital zircon U-Pb geochronology, detrital rutile U-Pb and trace element geochemistry, and sandstone petrography from sedimentary units across the Intra-Pontide suture. A major shift in provenance in the Paleocene-early Eocene caused by accretionary prism exhumation demonstrates that collisional stress from incipient İzmir-Ankara-Erzincan suturing could have been taken up by the Intra-Pontide suture. Furthermore, the sedimentary evolution of both suture zones reveals that the uplift and exhumation of the accretionary prism is an important signal of collisional geodynamics. Even though continental collisions assembled a larger landmass that favored trans-Tethyan mammalian dispersals, for 30 Myr after initial collision, collisional deformation did not form significant topography; marine barriers and endemism persisted until the late Eocene. Accretionary orogenies, like those in Anatolia, likely have an important control on biogeography. The findings presented in this dissertation bear on fundamental questions regarding the interconnectedness of Earth systems, including the effects of plate tectonics, the causes of topographic change, and the geologic drivers of biodiversity.

This book is the first contribution to the overview of Precambrian geology of China. It covers Precambrian geology of the North China Craton, the South China Craton and the Tarim Craton, as well as other smaller blocks in the Chinese orogenic belts. It provides systematic concepts of the Chinese paleo-continents and incorporates the most up-to-date achievements. Edited by many of the active researchers working at the forefront of the related fields, it contributes greatly to the international Precambrian geology community and would be of interest to geoscientists working in the research field of geology of China and Precambrian geodynamics.

This Proceedings volume contains selected papers from two symposia which were held during the 29th International Geological Congress, Kyoto, Japan, 24 August--3 September, 1992. The first symposium --- ''Reconstruction of the Paleo-Asian Ocean'' --- contains 11 papers from a group of scientists working together in an international project of the same name. The goal of the project is to collect and evaluate petrologic and tectonic data within specific terranes so as to understand the geodynamic processes leading to the amalgamation of Asia. These papers represent vital geological discussions for interpreting the geodynamic maps being produced by the project. From the second symposium of this volume --- ''Quaternary Environmental Change'' --- 14 papers were selected. The wide range of topics can be divided as follows: Deep sea core analysis; Coral reef and nearshore environment; Paleoenvironmental analysis; Tephras, Loess and Pedology; River morphology and others.

A compilation of landmark papers on granite petrogenesis is overdue. This volume is organized into a number of sections that represent what the editors regard as the main research fields in which progress has been made in understanding granites and their genesis. The origin of granitic magmas is part of the cycle that unites tectonic processes with the generation of mantle magma, crustal growth, the transfer of mantle heat to the crust, high-grade regional metamorphism, crustal melting and crustal differentiation. The extended subject area is far too wide to deal with in a single volume and therefore the selection has been limited to papers dealing with the formation, physical behaviour and chemical evolution of granitic magmas, and just touching on the matter of associated ore deposits. John (JC) Clemens and Fernando Bea are world experts on the subject of granite petrogenesis. Clemens' most important work has been on the origin and evolution of granites and silicic volcanic magmas, experimental studies and modelling of partial melting and the ascent and chemical evolution of granitic magmas, and these continue to be his main interests. Bea's research interests have been in the petrology and geochemistry of granite rocks and the mechanisms of generation of granite magmas, having studied in detail the role of heat-producing elements.

"Structural Geology has been taught, largely unchanged, for the last 50 years or more. The lecture part of most courses introduces students to concepts such as stress and strain, as well as more descriptive material like fault and fold terminology. The lab part of the course usually focuses on practical problem solving, mostly traditional me-thods for describing quantitatively the geometry of structures. While the lecture may introduce advanced concepts such as tensors, the lab commonly trains the student to use a combination of graphical methods like orthographic or spherical projection, as well as a variety of plane trigonometry solutions to various problems. This leads to a disconnect between lecture concepts that require a very precise understanding of coor-dinate systems (e.g., tensors) and lab methods that appear to have no common spatial or mathematical foundation. Students have no chance to understand that, for example, seemingly unconnected constructions like down-plunge projections and Mohr circles share a common mathematical heritage: they are both graphical representations of coordinate transformations"--Provided by publisher.